The present invention relates to surface finishing tools, such as are used for sanding, buffing, and polishing, and more particularly, to a system for easily and quickly attaching and removing a rotary finishing tool from the rotary power device used to drive the tool.
Rotary surface finishing tools, used to provide a wide variety of surface finishing functions including sanding, buffing, and polishing, are well known in the art. As used herein, the term xe2x80x9crotaryxe2x80x9d is meant to include orbitally driven finishing tools which, in most delicate finishing operations, are preferred because of the reduction in swirl marks in the finish on the workpiece. Such tools are typically circular in shape and are mounted on the drive spindle or arbor of a powered rotary or orbital driver which is held and manipulated by an operator. A wide variety of finishing tool mounting devices are known in the prior art, but one particularly desirable characteristic is to provide an assembly whereby the finishing tool may be quickly and easily mounted and removed from the power driver so that the operator can change tools with a minimum loss of time and with minimum effort. It is also important that a mounting system accurately center the rotary finishing tool on the axis of the power driver to maintain balance for high speed operation. It is also important to maintain positive driving contact between the driver and the finishing tool to avoid tool slippage and unbalance.
U.S. Pat. No. 4,907,313 shows a buffing pad attached to a cushioned back-up plate with the back-up plate attached directly to the drive spindle of a rotary driver. The pad and back-up plate are designed to provide self-centering attachment and actual attachment is provided by complimentary hook and loop fasteners on engaging surfaces of the pad and the back-up plate. Hook and loop fastener systems are widely used to attach rotary buffing pads, including dual action pads which combine rotary and orbital motion. Both types suffer from a common problem of fastener degradation as a result of heat buildup in the pad during operation. This can cause the pad to slip and move to an unbalanced off centered position or to even detach from the backing plate. Hook and loop fasteners are also known to degrade with washing and present a problem for pads intended to cleaning and reuse.
Another approach to attaching a rotary finishing tool to the drive spindle of a rotary operator is shown in U.S. Pat. No. 5,964,006. This attachment device uses an attachment nut that is threaded onto the shaft of the drive spindle, is automatically self-centering, and includes drive lugs on the pad which are engaged by the nut to help in attaching the pad and to drive the pad. The disadvantages of this assembly include the attachment nut which is exposed on the operating face of the pad and the need to thread and unthread the nut to mount and remove the finishing pad.
U.S. Pat. No. 5,138,735 shows a rotary buffing pad attachment device in which the pad has an internally threaded hub that is threadably attached to a complimentary externally threaded hub on the backing plate. The pad may be removed from the backing plate either by unthreading it or by utilizing the inherent resilience of the threaded plate hub to simply pull the buffing pad from threaded engagement with the hub. However, because the pad attachment to the hub is not positively locked, the pad may be inadvertently pulled off the hub if an obstruction is encountered in use. In addition, the pad attachment assembly requires complete threaded engagement to mount the pad and the use of a completely non-standard backing plate construction for the finishing pad.
In accordance with the present invention, an assembly for demountably attaching a rotary finishing pad or similar rotary finishing tool to the rotary drive spindle of a power tool includes a backing disc having a front face to which the rotary finishing tool is attached, either permanently or demountably, and a rear face that incorporates a first connector piece of a connector assembly for demountably attaching the backing disc to the front face of an annular backing plate. The backing plate, in turn, includes a drive hub that is adapted for driven connection to the drive spindle of a power tool. The front face of the backing plate includes a second connector piece for quick demountable attachment to the first connector piece on the rear face of the backing disc. The first and second connector pieces have complementary driving surfaces and complementary locking surfaces which respectively interengage in response to relative linear movement along their rotational axes of the backing disc into engagement with the backing plate, and relative radial movement between the locking surfaces with respect to said axes.
In the preferred embodiment, the backing disc has a circular outer peripheral edge and the backing plate has an annular ring of cushioning material attached to its outer peripheral edge, which ring of cushioning material has an inner peripheral edge that defines with the backing plate an annular recess dimensioned to receive the backing disc. The rotary finishing tool comprises a flexible circular disc having a generally flat rear face that is attached to the front face of the backing disc and, by virtue of the backing disc being recessed in the backing plate, the outer edge of the finishing tool extends radially outwardly into contact with the cushioning ring.
The locking surfaces on one of the two connector pieces are preferably deflectable in a radial direction with respect to the rotational axes to an unlocking position. In addition, the locking surfaces may be resiliently biased in an opposite radial direction to a locked position.
Preferably, the first connector piece comprises an integral unitary extension of the backing disc. In one embodiment, the first connector piece comprises a sleeve having its center axis coaxial with the backing disc and a plurality of oppositely disposed locking openings in said sleeve. In this embodiment, the second connector piece comprises a plurality of oppositely disposed locking projections that are resiliently biased into the locking openings in the sleeve and are manually retractable against said resilient bias from the locking openings. Preferably, the sleeve is annular in shape, and includes a pair of diametrically opposite driving slots positioned circumferentially spaced from the locking openings, and the second connector piece includes a pair of diametrically opposite driving projections circumferentially positioned to lie in and to engage said driving slots when the locking projections are aligned with the locking openings.
In another embodiment, the first connector piece sleeve is non-circular in shape, and the second connector piece comprises a frame piece having a non-circular shape and dimensioned to fit within said sleeve, the sleeve and the frame piece having abutting surfaces which form the driving surfaces.
In further embodiment, the sleeve on the rear face of the backing disc comprises a plurality of circumferentially spaced cylindrical first wall sections having inner and outer wall faces, each first wall section having a locking opening in one wall face and a first edge face between said wall faces, and said connector piece comprises a plurality of cylindrical second wall sections adapted to coaxially receive said first wall sections, each second wall section including an opposing wall face carrying one of said locking projections and a second edge face providing with said first edge face the driving surfaces. The locking openings in the first wall sections preferably comprise spherical recesses and the locking projections carried in the second wall sections comprise complementary spherical balls. The spherical recesses are preferably formed in the outer wall faces of said first wall sections and the spherical balls are mounted in retaining holes in said second walls sections for radial movement into locking engagement with said spherical recesses.